1. Field of the Invention
The present invention relates to submersible systems for monitoring and experimentation in aqueous ecosystems. More specifically, the present invention relates to a portable submersible in situ system for monitoring of, and experimentation with respect to coral reef ecosystems, coastal ecosystems and fisheries.
2. Related Art
The dangers to aqueous ecosystems from pollution and other processes are apparent, as is the need to act to preserve these ecosystems. Interest in gathering information on the processes and restoration of aqueous ecosystems, as well as interest in gathering information by experimentation on the effects of environmental perturbation on aquatic habitats, has greatly increased. This information is critical for assessing the health of aquatic ecosystems, for assessing environmental restoration progress, and for predicting the response of these ecosystems to climate change and declining water quality from natural and man-made influences.
In situ experiments measuring metabolic and geochemical processes associated with underwater organisms have been performed using very small ( less than 0.5 m diameter,  less than 4 liter volume) incubation chambers constructed of rigid Plexiglas or acrylic glass. These chambers effectively isolate a small volume of water about individual or small groups of underwater organisms enabling short-term (typically several minutes to a few hours) incubation experiments. These small chambers provide valuable information on processes associated with individual underwater species. However, accurate measurements of community level responses cannot be achieved using these small chambers. Additionally, these small chambers are not versatile and cannot be adjusted for size or volume to accommodate variations in substrate topography. These rigid chambers are limited in size due to difficulties in transporting and deploying larger chambers and in conforming and sealing the chambers to the often uneven substrate.
Community scale measurements of metabolic and geochemical processes have generally been performed using a technique called the xe2x80x9cupstream/downstreamxe2x80x9d approach. This technique measures spatial geochemical changes in the water column along transects (generally greater than 100 m) across the substrate at the upstream and downstream ends of each transect. Currents/water circulation at the study site must be well characterized using current meters or other water mass tracking techniques. This method assumes conservation of water mass along transects, and is, therefore, limited to areas where unidirectional currents can be identified. Difficulties in accurately tracking the movement of a water mass result in the potential for a large margin of error. Many coastal ecosystems, such as coral reefs, have a complicated topography resulting in complex water circulation patterns. Thus, use of this technique is severely limited in its application.
Twenty-four hour monitoring along transects is logistically difficult due to problems in navigating along transects during dark hours. Most importantly, the upstream/downstream technique is limited by the resolution of geochemical measurements. Water must reside over the substrate long enough for its chemistry to be affected by processes of interest. Faster water flow rates result in shorter residence times and require a higher resolution for geochemical measurements to detect smaller chemical changes. Slower flow rates increase residence time of water over the substrates but most underwater organisms alter their metabolism when flow rate decreases, producing an abnormal response.
Structures resembling tunnels have been used to divert water flow in a modified upstream/downstream method. However, it has been found to be difficult to divert water flow over the long distances (100""s of meters) typically required for accurate geochemical measurements with this method.
Therefore, there is a need in the art for a system that is portable, yet capable of accurately monitoring underwater habitats of various topography and currents therein at the individual organism, or community level.
According to the present invention, a portable system is provided for isolating, in situ, a large volume of water overlying a substrate in various aqueous environments. The system is designed to isolate the volume of water from the ambient aquatic environment, while maintaining contact between the captured volume of-water and the substrate components beneath it, including sediments and living organisms. The system provides for situ monitoring of physical and chemical characteristics of the water volume, monitoring of the components of the water, and associated monitoring of underwater organisms and substrates. Additionally, the system can be used for in situ manipulation of the physical and chemical parameters within the isolated volume of water for experimental investigations on the effects of environmental disturbances of the water, disturbances of components of the water, and disturbances of.the substrate.
In accordance with the invention, a submersible system is provided for isolating a volume of water located above an underwater substrate and for analyzing the volume of water, the system comprising: a tent having a shape enclosing an area of underwater substrate and a volume of water immediately above the substrate; support means for maintaining the shape of the tent; securing means for securing the tent to the substrate; a circulation system, located at least partially within the tent, for circulating the volume of water within the tent so as to maintain a circulating flow pattern within the tent; and a flow through analytical system for removing a portion of water from the enclosed volume of water, and for analyzing at least one property of the portion of water.
Preferably, analytical system includes means for returning the portion of water to the volume of water within the tent.
Advantageously, the submersible system further comprises means for removing trapped air from the tent.
Preferably, the tent further comprises a tent covering of a clear plastic material and at least one clear plastic tent door located at one end of the tent. Advantageously, the tent includes a further tent door located at the opposite end of the tent and the tent doors are attached by respective zippers to the tent covering. In a preferred implementation, the tent covering and the tent doors are comprised of a clear polyvinyl material. Preferably, the tent further comprises a bottom covering directly positionable on the substrate so as to separate the substrate from the volume of water.
The tent covering preferably includes a bottom peripheral flap extending outwardly therefrom so as to be positionable flat on the substrate and the securing means preferably comprises weight means positionable to provide weighing down of the flap so as to secure the flap in place. In one preferred implementation, the weight means comprises a plurality of sand bags, while in another, the weight means comprises a chain. In advantageous implementation, the flap comprises a reinforced flap extending outwardly from the bottom of the tent around the entire perimeter of the tent. In this implementation, the securing means advantageously comprises a plurality of sandbags located on top of the reinforced flap or a chain secured to the reinforced flap.
In a preferred embodiment, the support means comprises a tent frame comprising: a frame base for defining the substrate area enclosed by the tent; a plurality of frame ribs; a plurality of fittings on the frame base for attaching the frame ribs to the frame base; a frame spine; and a plurality of fittings on the frame spine for attaching the frame ribs to the frame spine. Advantageously, the frame base and frame spine each comprise a plurality of sections for enabling assembly and disassembly thereof. Preferably, the tent frame further comprises a plurality of metallic rods located within the frame base for assisting in maintaining the position of the frame upon the substrate. In this implementation, the frame base, the frame spine and the metallic rods each preferably comprise a plurality of sections for enabling assembly and disassembly thereof. Advantageously, the frame base, the frame ribs and the frame spine are comprised of polyvinyl chloride. Preferably, the frame base further comprises a plurality of pivoting stake supports. In a preferred implementation, the frame spine fittings comprise 90 degree fittings and the frame base fittings comprise T-fittings.
Other features and advantages of the invention will be set forth in, or will be apparent from, the detailed description of the preferred embodiments which follows.